1. Technical Field of the Invention
The present invention relates in general to the telecommunications field and, in particular, to a method and apparatus for mobile radio telephone users to communicate via the Internet.
2. Description of Related Art Today's cellular networks are designed to interconnect and interoperate with both Public Switched Telephone Networks (PSTNs) and Integrated Services Digital Networks (ISDNs). A common characteristic of these networks is that they are circuit-switched networks that handle relatively narrow bandwidth traffic.
In contrast, the rapidly growing "IP Network" or "Internet" is a packet-switched network which handles much wider bandwidth traffic than the circuit-switched networks. As such, most conventional wire-bound communications terminals are capable of fully utilizing the Internet's much wider bandwidths. However, a problem with using wireless (e.g., cellular) radio terminals to communicate with the Internet is that the wireless terminals are bandwidth limited by their respective radio air interfaces. A similar problem exists for Asynchronous Transmission Mode (ATM) or broadband ISDN communications systems, if these systems are being accessed by wireless radio terminals. Therefore, there is a need to overcome the bandwidth limitations of conventional wireless radio terminals, so that future wireless radio terminals can be utilized with packet-switched networks (or other wideband networks) to handle wideband traffic comparable to that handled by wire-bound terminals.
The air interface standards originally promulgated for cellular radio networks had been developed based on the use of specialized speech coding techniques. These coding techniques were optimized to allow the transmission of biteffective, two-way speech traffic over the radio air interface. Subsequently, the air interface standards for cellular networks were modified to allow the transmission of relatively low speed data over the radio air interface. Now these standards also allow both the uplink and downlink transmissions of packet data, with coding optimized for these types of transmissions. An example of such a packet data standard is the General Packet Radio Service (GPRS) Radio Interface for the Global System for Mobile Communications (GSM), which is described in GSM Technical Specification 04.60 published by the European Telecommunications Standards Institute (ETSI).
Notably, bandwidth requirements are asymmetrical for many telecommunication network applications. In other words, the information being transferred to a terminal (e.g., via the downlink in a radio environment) typically requires much more bandwidth than the information being transferred from the terminal (e.g., via the radio uplink). An example of such an asymmetrical application is the so-called "Video-On-Demand" (VOD) application, wherein the amount of data used to make a request for video (sent over the uplink) is relatively small in comparison to the large amount of video data sent in return (over the downlink). Consequently, in order to optimize these asymmetrical applications, the air interface protocols for such services as the Digital Video Broadcast (DVB) and Digital Audio Broadcast (DAB) are being standardized so these services can be provided.
In summarizing the current state of the art, there are a number of radio interface standards that are either in existence or being devised (e.g., GSM, DAB/DVB, etc.). Also, there are numerous methods being used to code information transmitted over particular air interfaces (e.g., speech coding in the GSM, or packet data handling in the GPRS). Consequently, in the future, all of the bandwidth requirements for these different standards and coding techniques will need to be considered and effectively optimized.
In contrast, in a strictly Internet environment, there is only one protocol needed (e.g., the IP network standard) to prescribe how information should be transmitted over the packet-switched network, because there is no such air interface bandwidth problem there. However, another significant problem arises in attempting to access a packet-switched, land-based network (e.g., Internet) with a wireless radio terminal, because of the difficulties encountered in transmitting wide bandwidth traffic over the radio links, and the different speech coding techniques involved.
For example, as mentioned above, one such problem is encountered when wide bandwidth traffic (e.g., from the Internet) is to be transmitted over the downlink radio air interface to a wireless radio terminal. Certain radio air interfaces, such as those used in the GSM and DAB systems, can provide the necessary downlink bandwidths required for typical applications used in packet-switched, land-based networks. However, the problem that remains is that there is no method available for use in combining the different interfaces involved.
In a cellular mobile radio network, a subscriber can "surf" the World-Wide Web (WWW) via the Internet by using a "laptop" personal computer (PC) as a radio terminal. The subscriber's search instructions can be readily conveyed over the uplink via the cellular network's radio air interface to a Mobile Services Switching Center (MSC). The instructions are then conveyed over the Internet via an Internet-connected server in accordance with the appropriate IP Standard protocol. However, in contrast, a much larger amount of information is conveyed over the downlink, and consequently, the process of transmitting such information over the radio link of a conventional cellular network is much too slow and thereby unacceptable to a subscriber, when compared to the much higher throughput of a typical wire-bound terminal.
The second problem is encountered when speech information is to be conveyed from a wireless radio terminal to the Internet. The transmission of speech information over a radio air interface is best accomplished by using a cellular circuit-switched connection. An example of such a connection is a Traffic Channel (TCH) in the GSM. On the other hand, the transmission of low speed data over a radio air interface is best accomplished by using a cellular packet-switched connection. An example of such a connection is a Packet Data Traffic Channel (PDTCH) in the GPRS. As such, while it is usually preferable to transmit speech and data over the air waves via different radio channels with specialized coding, the corresponding speech and data information can be conveyed over the Internet using a single packet data connection. Consequently, there appears to be no particular bandwidth problem for applications on the Internet that convey speech and low speed data. Nevertheless, there is still a problem associated with the process of selecting appropriate channels and procedures to be used for transcoding and conveying speech and low speed data between the packet-switched and cellular radio networks.